In the HMP shunt, oxidative phase, which enzyme catalyzes the committed, rate-limiting, and NADPH-producing first step, and what is its key allosteric inhibitor?
- A 6-phosphogluconate dehydrogenase; NADPH
- B Glucose-6-phosphate dehydrogenase (G6PD); NADPH ✓
- C Transketolase; AMP
- D Glucose-6-phosphate dehydrogenase (G6PD); ATP
Correct answer: B. Glucose-6-phosphate dehydrogenase (G6PD); NADPH
Explanation
Glucose-6-phosphate dehydrogenase (G6PD) catalyzes the first and rate-limiting step of the HMP shunt, generating NADPH. NADPH itself is the principal product-feedback inhibitor, reducing enzyme activity when cellular NADPH is adequate. G6PD deficiency is the most common enzyme deficiency worldwide and leads to hemolytic anemia under oxidative stress (e.g., primaquine, fava beans) because erythrocytes cannot regenerate glutathione.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.